In subterranean formations of oil and gas wells, the formation may have insufficient stress barriers to contain hydraulic fractures made within the producing zone. This can lead to inefficient fracturing, with much of the treatment potentially stimulating bare rock. Vertical fracture growth out of the hydrocarbon bearing portions of the formation, either up or down, may result from hydraulic fracturing in such formations having little or no stress contrast between the formation layers. A particular problem encountered in formations where there are insufficient stress barriers is the fracturing or stimulation of water or undesirable gas producing zones.
Containment of these undesirable fractures has been accomplished in the past by placing an artificial barrier along the boundaries of the fracture to prevent further fracture growth out of the producing zone. Known methods for containing fracture growth include placing of proppants and fluids with different densities in the fracture to limit the undesirable fracture growth. The main drawback to such techniques is the difficulty of providing proper barrier placement such that the prior art methods are unreliable.
In drilling operations, undesirable fractures may form in areas adjacent to the well bore resulting in the lost circulation of drilling fluid. Eventually, in highly permeable formations, fluid is lost from the drilling fluid within the fracture so that the mud consequently becomes dehydrated and blocks the fracture so that there is no transmission of pressure to the tip of the fracture and further fracture propagation is prevented. In shale or low permeability formations, however, where there is little or no fluid loss to the formation, the fracture tends to keep propagating, particularly when using high pressure or high density drilling fluids.
There is therefore a need to provide improvements in compositions and methods used for containing such fractures.